Thermal radiation sensor

ABSTRACT

An instrument sensor member has positioning means to establish a fixed relationship between the member and a small selected area of a living organism. Thermal radiation flux from the area impinges on a concave surface on the member and is reflected to a radiometer fixed at the focus of the surface. The thermal radiation provides a measure of the temperature of the blood in the vessel or vessels immediately under the surface of the area which may be the tympanic membrane as disclosed herein.

United States Patent [72] Inventor EdwardC.Wortz Northridge, Calif. 1211AppLNo. 665,396 [22] Filed Sept. 5, 1967 [45] Patented June 1,1971 [73Assignee The Garrett Corporation Los Angeles, Calif.

[54] THERMAL RADIATION SENSOR 6 Claims, 13 Drawing Figs.

52 use 73/35511, l28/2R [51] lnt.Cl G0lj5/06, G0lkl/l4 [50] Field ofSearch {56} References Cited UNITED STATES PATENTS 2,813,203 11/1957Machler 73/355X 3,274,994 9/1966 Sturm 128/2 3,282,106 1 1/1966Barnes... 73/355 3,309,236 3/1967 Gunji 73/355X Primary Examiner-LouisR. Prince Assistant Examiner-Frederick Shoon Att0rneys-0rville R.Seidner and H. Vincent Harsha ABSTRACT: An instrument sensor member haspositioning means to establish a fixed relationship between the memberand a small selected area of a living organism. Thermal radiation fluxfrom the area impinges on a concave surface on the member and isreflected to a radiometer fixed at the focus of the surface. The thermalradiation provides a measure of the temperature of the blood in thevessel or vessels immediately under the surface of the area which may bethe tympanic membrane as disclosed herein.

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ENTOR. EDWAR .WORTZ AGENT THERMAL RADIATION SENSOR BACKGROUND OF THEINVENTION This invention is directed generally to apparatus, method, andtechnique of measuring the thermal radiation flux from a small selectedarea of a living organism, and is more particularly concerned with themeasurement of the temperature of the blood coursing the arteries, veinsor capillaries immediately underlying the selected area. Specifically,for the instant application of the invention as disclosed herein, theinvention is concerned with the measurement of blood temperature bythermal radiation therefrom through the tympanic membrane.

It is already known that the hypothalamus provides the thermoregulatoryfunction of the human body. Furthermore, there is convincing evidencethat the hypothalamus is a receptor organ which performs itsthermoregulatory function as a consequence of the body temperaturesensor signals" it receives from the blood supplied .to it via thecarotid artery, and that the temperature regulation occurs at a strictlydetermined set point. Since the carotid artery also furnishes the bloodsupply for the capillary vessels in the tympanic membrane, it has beensuggested that a more precise and nearly exact measure of the mostmeaningful temperature of the human body would be obtained if themeasurement were made at the tympanic membrane.

To this end there is known in the prior art a thermometerlike deviceadapted to be inserted in the external acoustic meatus or ear canal, theend of the device being brought to bear lightly against the tympanicmembrane in order to obtain a measure of the temperature thereat by theusual method of direct conduction from the membrane. This prior artdevice has been employed principally in clinical research programs sinceit is subject to a number of drawbacks and disadvantages which preventroutine employment at the layman or semiskilled level.

The principal disadvantage of the aforesaid prior art device is that thetympanic membrane is a sensitive tissue, and any foreign object bearingagainst it results in discomfort and/or pain to the individual, andvertigo for a large percentage of the population, as well as attenuatedacoustic response of the eardrum over the entire audible-spectrum. Thentoo, the membrane is easily punctured or other wise injured by thehighly localized pressure exerted against it by the small thermistor orthermocouple such as is usually employed, hence the use of the aforesaiddevice can be made only under very strictly controlled procedures byhighly skilled and trained workers.

It will be noted that the employment of any device which depends uponconduction from a tissue surface is made more difficult in the casewhere the tympanic membrane is the tissue, due to the fact that the earcanal leading to the tissue is narrowest at its middle, and is not atall straight but is directed inward, forward, and upward and then inwardand backward to the membrane. Consequently, there is never any assurancethat the small thennistor or thermocouple boll is optimally positionedeven by trained and highly skilled persons.

SUMMARY OF THE INVENTION Contrasted with the devices of the prior art,the present invention provides the means and method of sensing thetemperature of the blood in the tympanic membrane by radiation therefromto a radiometer, thereby eliminating all necessity for contact with themembrane. Since the mass of the radiometer is extremely small, the timeconstant is correspondingly low, of the order of 0.1 second or less.Furthermore, since there is no contact of the membrane by theradiometer, the normal audio function of the ear remains substantiallyunimpaired. This last mentioned feature is of particular importance incases where it is desired to communicate orally with the subject, forexample by way of a single earphone disposed over the pinna or auricleof the ear within which the radiometer sensor is disposed. In addition,the configuration of the device according to the present invention issuch that there is no undesirable discomfort or pain resulting frominsertion of the device into the ear canal, and the medical andphysiological hazard is eliminated.

It should also be noted that inasmuch as the device utilizes radiationflux to provide the measure, it is independent of environmentalatmospheric conditions. Desirably, the wavelength range of the radiationutilized by the device is of the order of9 to 10 microns, i.e. theinfrared range, since it is then possible to detect temperature changesof the order of 0.05 C. Sensitivity of this order is desirable inasmuchas the meaningful temperature differences are very small. In a typicalcase the maximum temperature variation could be expected to be about 3C.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation view,approximately full scale, ofa right ear of a human body with oneembodiment of the invention disposed therein;

FIG. 2 is a semidiagrammatic section view of the ear anatomy takengenerally on the line 22 of FIG. 1;

FIGS. 3, 4 and 5 are top, end and side views respectively of theembodiment of the invention;

FIG. 6 is an approximate 4X enlarged section view taken on the line 6-6of FIG. 4;

FIG. 7 is an end elevation view of a second embodiment of the invention;

FIG. 8 is a side elevation section view taken on the line 8-8 of FIG. 7,and enlarged about 4X;

FIG. 9 is an end elevation view of a third embodiment of the invention;

FIG. 10 is a side elevation section view taken on the line 10-10 of FIG.9, and enlarged about 4X;

FIG. 11 is another semidiagrammatic section view in elevation, similarto FIG. 2 and showing a fourth embodiment of the invention disposed in ahuman right ear; I

FIG. 12 is an end elevation view of the embodiment illustrated in FIG.II, and

FIG. I3 is a side elevation section view taken on the line 1343 of FIG.12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. I and 2there is shown an instrument 20 disposed within the right outer car 22of a human being. As is well known, the ear 22 comprises the pinna orauricle 24 and the external meatus, or auditory canal 26 across theinner end of which is disposed the tympanic membrane, or eardrum 28. Theauricle 24 consists of a plate of elastic cartilage, folded and bentupon itself to form ridges and depressions, one of the ridges definingthe concha 30 which is prolonged inward to form the outer two-fifths ofthe canal 26.

As shown in FIGS. 3-5, the instrument or sensor 20 comprises a bodyhaving an enlarged body portion 32 which merges with a reduced sectionprobe portion 34 which is somewhat elongate to lie within the ear canal.The body portion 32 is configured to fit snugly within the concha 30 ofthe ear, and to that end is provided with a tab 36 which lies within theupper curved portion of the concha and under the partially overlyingridge 38. As is now evident, the sensor 20 is very nearly identical to,and may be easily fabricated along the lines of, the familiar ear moldor earplug which is utilized in the hearing aid art. Preferably, thesensor is fabricated from one of the familiar plastic materials known asLucite.

Two small passageways 40 and 42 traverse the sensor from end to end asbest seen in FIG. 6. Passageway 40 is unobstructed to provide ambientair pressure access to the tympanic membrane 28 in cases where thesensor 20 is employed under conditions of changing atmospheric pressure.The distal end of passageway 42 opens on to a chamber defining a concavesurface 44 formed in the end of the probe portion 34. Preferably, thesurface 44 is paraboloidal with a radiometer 46 disposed at its focus soas to be subject to the radiation flux which is directed on to thesurface 44 from the tympanic membrane 28 when the sensor 20 is disposedin the car as shown in FIG. 2.

As will be appreciated, in order for the surface 44 to function for itsintended purpose, it should be highly reflective. To this end it may becoated with a highly reflective coating of gold or aluminum and this maybe accomplished by vacuum deposition or sputtering. In the alternative,a thin metal shell of paraboloidal cup may be formed by drawing orcasting with the concave surface given a subsequent polishing, afterwhich the shell is cemented or other wise bonded into place within thechamber.

The radiometer 46 may be comprised of a thermistor, bolometer orthermocouple, and is provided with a pair of conductor leads 48 whichare disposed in the passageway 42 leading from the radiometer 46 to theexterior of the sensor 20 where the conductors 48 may be coupled to asuitable amplifier and galvanometer means calibrated to readtemperature, all as well understood by those skilled in the art andneeding no further amplification herein. In order to insure retention ofthe radiometer 46 at the focus of the surface 44 a small drop of plasticcement 50 or the like is disposed at the inner orifice of the passageway42. Likewise, another small drop of cement 52 may be disposed adjacentthe outer orifice of the passageway to affix the conductors 48 thereat.As an alternative, the conductors 48 may be fixedly disposed within asmall plastic tube or sleeve which has a length that extends from theradiometer 46 to the exterior face 54 of the sensor body portion 32. Inthis case the passageway 42 would have a cross section just slightlylarger than that of the exterior of the plastic tube or sleeve to enablethe tube and enclosed conductors to be slidably received within thepassageway until the radiometer is positioned exactly at the focus ofthe concave surface 44.

A window or transparent shield 56, comprised for example of apolyethylene plastic which transmits infrared radiation flux, may bedisposed over the end of the probe portion 34 to protect the radiometer46 and the reflective surface 44 against hair, earwax or the like.

As depicted in the embodiments of FIGS. 1-6, the sensor 20 is arelatively rigid apparatus configured to fit into the outer ear afterthe manner of a hearing aid ear mold, and it is now apparent that thebody portion 32 and probe portion 34 constitute means for affixedlyspacing the concave surface 44 in a predetermined spaced relationship tothe tympanic membrane 28. Preferably, of course, the surface 44 shouldbe so disposed as to be subject to radiation flux from substantiallyonly the tympanic membrane, since any radiation from the walls of theinner end of the ear canal would reflect to a large extent thetemperature condition of the bony structure surrounding the canal andhence would tend to mask the desired tube reading obtainable from thetemperature of the blood in the tympanic membrane. To a large extent,this limitation can be compensated for be designing the paraboloidsurface with a configuration which is relatively deep into the probeportion 34 as compared with its open end diameter. Furthermore,compensation may be had by designing the paraboloid surface such thatthe focus is very close to the vertex of the parabola in which case theradiometer 46 will be subject to only a minimum of stray radiation fluxfrom the wall of the ear canal.

In a typical embodiment the diameter of the window of the paraboloidsurface would be of the order of mm., and the depth would be about 7 mm.

In the embodiment illustrated in FIGS. 7 and 8 the sensor 60 comprises ahollow elongate tubular member 62 which has a fair degree of rigidityagainst bending and compressing forces, and which may be comprised of anacrylic or polyvinyl chloride plastic material. Alternatively, thetubular member may be formed of metal tubing or of a hard rubber tubingmaterial. Preferably the tubular member 62 is about 6 mm. in diameterand about mm. long.

Disposed approximately equidistantly along the outer surface of member62 are three thin flexible rubber discs 64, 66 and 68 of progressivelylarger diameter from right to left as seen in the Figure. The small disc64 is preferably about 15 mm. in diameter while the larger disc 68 isabout 20 mm. The intermediate disc 66 is sized between that of the othertwo discs. Secured within one end of the tubular member 62 is plug 70provided with a pair of radially extending integral tabs 72, 74 whichassist with the insertion of the sensor 60 into, and removal from, theear canal. The plug 70 and integral tabs may be of soft rubber or thelike.

Secured within the other end of the tubular member 62 is a paraboloidalshell or cup 76 provided with a polished reflective surface, asdescribed aforesaid in connection with surface 44 of FIG. 6; anddisposed at the focus of the cup 76 is a radiometer 78 fixedly securedthereat by its conductors 80, 82 which extend over the front edge of thecup 76 at diametrically opposite points, and back along the inner wallof the tubular member 62. The plug 70 is provided with a passageway 84from which the conductors 80, 82 emerge for coupling to externalapparatus A plurality of pressure-relief passageways 86, 88 and 90traverse the discs 64, 66 and 68 so that when the sensor 60 is insertedin the car, there will be no air-bound chamber adjacent the exteriorface of the tympanic membrane. This feature permits the sensor 60 to beused in situations where ambient pressure may be fluctuating withinrelatively wide range limits, as for example in aircraft of otheraerospace vehicles.

A polyethylene shield 92 may be disposed over the end of the tubularmember 62 to protect the surface of the cup 76 and the radiometer 78.

The sensor 60 is readily insertable into the car without discomfort onthe part of the wearer since the discs 64, 66, 68 are very flexible andtend to accommodate and bend back upon themselves as necessary in orderto conform to the restriction and configuration of the ear canal.

The embodiment of FIGS. 9 and 10 is similar to that of FIGS. 7 and 8with the sole exception that the discs 64, 66 and 68 of the latter arereplaced by a closed-cell foam plug 94 which may be fabricated fromfoamed rubber or polyurethane material. A small passageway 96 traversesthe plug 94 from end to end to provide ambient air-pressure relief. Aswill be noted, the plug 94 is generally frustoconical in configurationso as to be received neatly, finnly and comfortably within the earcanal.

The structure 100 of the sensor embodiment illustrated in FIGS. "-13differs somewhat from the preceding embodiments in that sensor 100 iscomprised of the tubular member 102 which may be fabricated of arelatively soft resilient rubber with a small longitudinal tubularpassageway 104 opening at one end upon the-concave surface 106. Aradiometer 108 is disposed at the focus of the portion 106 which ispreferably configured as ensuing paraboloid with a coated surface whichis highly reflective to thermal radiation flux. Conductor leads 110 inthe passageway 104 support the radiometer 108 at one end thereof, theother ends of the conductors being adapted to being coupled to externaltemperature-indicating apparatus as aforesaid.

Spaced at angular intervals around the outer periphery of the member 102are a number of rails 112 formed integrally with the member 102. Theradially disposed rails 112, shown here as being six in number, extendlongitudinally, sloping generally outwardly of the axis of the member102 from the detector end 114 thereof, joining the distal end 116 asshown.

In a typical embodiment according to FIGS. 12, 13, the tubular member102 would be about 15 mm. long and about 6 mm. in diameter. The overalldiameter across the rails 112 at the greatest distance from the member102 would be about 10 mm. The rails 1 12 act as position retentionmembers which by virtue of their collapsible wedging action, asillustrated in FIG. I], serve to position and retain the sensor 100 inthe ear canal.

Iclaim:

1. A sensor for sensing thermal radiation from a tympanic membrane of ahuman body, comprising:

a. sensor body means having an elongate probe portion adapted to bedisposed in an ear canal of the human body with one end of said probeportion adjacent a tympanic membrane of the body, said end of said probeportion defining a concave surface;

b. thermal radiation flux converging means on said body I meansincluding a radiation reflective surface means on said concave surfaceadapted to gather thermal radiation flux from a portion of the adjacenttympanic membrane and direct said flux to a small volume of space;

c. a radiometer disposed in said volume of space; and

d. spacing means on said sensor body means for affixedly spacing saidflux-converging means in a predetermined spaced relationship to theadjacent tympanic membranes such that thermal radiation flux from theadjacent tympanic membrane is converged on said radiometer by saidconverging means, said spacing means comprising resilient element meansdisposed exteriorly along said probe portion to engage the ear canalwith said probe portion spaced substantially centrally therealong.

2. The sensor of claim I in which said reflecting concave surface hasthe configuration of a paraboloid of revolution, and said radiometer isdisposed at the focus thereof.

3. The sensor of claim 1 in which said resilient element means compriseaplurality of thin flexible resilient discs substantially equidistantlyspaced along said probe portion.

4. The sensor of claim maker in which said resislient element meanscomprise a closed-cell foam plug of generally frustoconicalconfiguration.

5. The sensor of claim 1 in which said resilient element means comprisea plurality of soft resilient rails extending longitudinally along saidprobe portion and spaced radially outwardly therefrom.

6. Apparatus for sensing thermal radiation from a tympanic membrane ofahuman body, comprising:

a. body means having an elongate probe portion adaptedto be disposed inan ear canal of the human body with one end of said probe portionadjacent a tympanic membrane of the body, said body means having acup-shaped chamber with an opening adjacent said one end of said probeportion, said chamber having a surface reflective to thermal radiation.

b. a radiometer disposed in said chamber and spaced from said opening;said surface reflecting radiation from said opening onto saidradiometer, and

c. means for'shielding said radiometer from heat radiation emitted bysaid ear canal.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 581,570 Dated June 1, 1971 Inventor(s) Edward C. Wortz It is certified thaterror appears in the aboveidentified patent and that said Letters Patentare hereby corrected as shown below:

Column 6, line 1, change "maker" to --l--; same line correct spelling of"resilient" Signed and sealed this 28th day of March 1972.

(SEAL) Attest:

EDWARD M.FLEI'CHER,JR. ROBERT GOT'I'SCHALK Attesting OfficerCommissioner of Patents FORM F'O-1050 (10-69) USCOMM-DC 60376-P69 15 U SGOVERNMENT PIHNTING OFFICE ISIS 0-366-334

1. A sensor for sensing thermal radiation from a tympanic membrane of ahuman body, comprising: a. sensor body means having an elongate probeportion adapted to be disposed in an ear canal of the human body withone end of said probe portion adjacent a tympanic membrane of the body,said end of said probe portion defining a concave surface; b. thermalradiation flux converging means on said body means including a radiationreflective surface means on said concave surface adapted to gatherthermal radiation flux from a portion of the adjacent tympanic membraneand direct said flux to a small volume of space; c. a radiometerdisposed in said volume of space; and d. spacing means on said sensorbody means for affixedly spacing said flux-converging means in apredetermined spaced relationship to the adjacent tympanic membranessuch that thermal radiation flux from the adjacent tympanic membrane isconverged on said radiometer by said converging means, said spacingmeans comprising resilient element means disposed exteriorly along saidprobe portion to engage the ear canal with said probe portion spacedsubstantially centrally therealong.
 2. The sensor of claim 1 in whichsaid reflecting concave surface has the configuration of a paraboloid ofrevolution, and said radiometer is disposed at the focus thereof.
 3. Thesensor of claim 1 in which said resilient element means comprise aplurality of thin flexible resilient discs substantially equidistantlyspaced along said probe portion.
 4. The sensor of claim maker in whichsaid resislient element means comprise a closed-cell foam plug ofgenerally frustoconical configuration.
 5. The sensor of claim 1 in whichsaid resilient element means comprise a plurality of soft resilientrails extending longitudinally along said probe portion and spacedradially outwardly therefrom.
 6. Apparatus for sensing thermal radiationfrom a tympanic membrane of a human body, comprising: a. body meanshaving an elongate probe portion adapted to be disposed in an ear canalof the human body with one end of said probe portion adjacent a tympanicmembrane of the body, said body means having a cup-shaped chamber withan opening adjacent said one end of said probe portion, said chamberhaving a surface reflective to thermal radiation. b. a radiometerdisposed in said chamber and spaced from said opening; said surfacereflecting radiation from said opening onto said radiometer, and c.means for shielding said radiometer from heat radiation emitted by saidear canal.